The proposed research is designed as a study of the effect of crevicular dental plaque on the systemic immune capacity of the host. We will attempt to determine what effect the continued antigenic insult of oral microorganisms associated with periodontal tissues has on the relative state of immune competency of medically healthy adults afflicted with varying levels of chronic periodontal disease. Similar studies will be conducted with adults who have periodontal disease but who are receiving professional treatment and who are practicing acceptable levels of plaque control through home care. Multiple clinical measurements of the severity of periodontal disease and of the level of oral hygiene over a two-year period will be taken. These clinical indexes will be evaluated with respect to laboratory measurements of the patients' lymphocyte responses (transformation) to various selected stimuli.